Field of the Invention
The present invention relates to a crank chamber internal pressure reduction mechanism for internal combustion engine.
Description of the Related Art
Some saddle-ride type vehicles such as motorcycles include a crank chamber internal pressure reduction mechanism that forcibly suctions emissions such as blow-by gas and engine oil in a crank chamber of a crankcase and discharges the emissions outside the crank chamber.
A motorcycle disclosed in Patent Document 1 discloses an oil pump structure for internal combustion engine. The oil pump structure disposes a scavenging pump at a bottom of a crank chamber, which is formed by joining right and left crankcases, at the center in a right-left direction. Since the scavenging pump suctions and discharges oil in the crank chamber via a suction oil passage, the oil in the crank chamber can be efficiently discharged from the center at the bottom of the crank chamber.
Patent Document 1: Japanese Laid-open Patent Publication No. 2009-121326
However, disposing the scavenging pump as the crank chamber internal pressure reduction mechanism that forcibly suctions the emissions and discharges the emissions outside the crank chamber like Patent Document 1 increases the number of components, making the mechanism complicated. Additionally, a space to dispose the scavenging pump needs to be disposed in the crankcase. This increases a size in crankcase, thereby causing a problem of falling to reduce the weight.